Reaction of hexanuclear niobium and tantalum halide clusters with mercury(Ⅱ) halides.Ⅱ. Semiconducting compounds with [Ta6CI12]3+ unit

摘要

A series of paramagnetic clusters of thecomposition [(Ta6CI12)CI(H2O)5][HgX4]·9H2O (X = CI, Br,I) has been prepared by the reaction of [Ta6CI12]3+methanol-water solutions with HgX2 and NaX halides. Thestructure of [(Ta6CI12)CI(H2O)5][HgBr4]·9H2O has beensolved by X-ray diffraction in the cubic space group Fd3m.Crystal data: a = 20.036(2) ?, V = 8043.0(1) ?3, Z = 8,R = 0.048(Rw=0.051). The Structure is composed of anoctahedral [(Ta6CI12)CI(H2O)5]2+ cluster cation,tetrahedral [HgBr4]2- anion and crystal water molecules.The 2mm symmetry of the octahedron is reduced by thestatistical distribution of the five water molecules,O(1), and chlorine , CI(2), at the terminal coordinationsites. Thus, the distances Ta-O(1) and Ta-CI(2) areaveraged to the value of 2.32(2)?. The Ta-Ta and Ta-CI(1) bond distances are 2.911(1) ? and 2.440(3) ?,respectively, whereas the Hg-Br bond distance is 2.564(3)?. The cluster [(Ta6CI12)CI(H2O)5][HgBr4]·9H2O issemiconducting with two levels governing conductivitywith respective activation energies, Ea1 = 0.24 eV and Ea2 = 0.17eV.